From 4c1bff5b969eedb36691d06b0a0f113025e50100 Mon Sep 17 00:00:00 2001
From: Michael Bock <me@thought2.de>
Date: Fri, 25 Jun 2021 06:02:01 +0200
Subject: [PATCH 1/2] Add match function to Json module

---
 src/Json.ts  | 45 +++++++++++++++++++++++++++++++++++++++++++++
 test/Json.ts | 11 +++++++++++
 2 files changed, 56 insertions(+)

diff --git a/src/Json.ts b/src/Json.ts
index fd2acbbb8..9ea53e798 100644
--- a/src/Json.ts
+++ b/src/Json.ts
@@ -60,3 +60,48 @@ export const parse = (s: string): Either<unknown, Json> => parseJSON(s, identity
  */
 // tslint:disable-next-line: deprecation
 export const stringify = <A>(a: A): Either<unknown, string> => stringifyJSON(a, identity)
+
+// -----------------------------------------------------------------------------
+// destructors
+// -----------------------------------------------------------------------------
+
+/**
+ * Takes a function for each possible Json type and returns the result of the one from the position that matches the given data.
+ *
+ * @category destructors
+ * @example
+ * import * as J from 'fp-ts/Json'
+ *
+ * const typeOf = J.match(
+ *   () => 'null',
+ *   () => 'boolean',
+ *   () => 'number',
+ *   () => 'string',
+ *   () => 'array',
+ *   () => 'object'
+ * )
+ *
+ * assert.deepStrictEqual(typeOf(32.2), 'number')
+ * assert.deepStrictEqual(typeOf(['a', 'b']), 'array')
+ *
+ *  @since 2.10.6
+ */
+export const match: <Z>(
+  isNull: () => Z,
+  isBool: (x: boolean) => Z,
+  isNum: (x: number) => Z,
+  isStr: (x: string) => Z,
+  isArr: (x: Array<Json>) => Z,
+  isObj: (x: Record<string, Json>) => Z
+) => (j: Json) => Z = (isNull, isBool, isNum, isStr, isArr, isObj) => (j) =>
+  j === null
+    ? isNull()
+    : typeof j === 'boolean'
+    ? isBool(j)
+    : typeof j === 'number'
+    ? isNum(j)
+    : typeof j === 'string'
+    ? isStr(j)
+    : Array.isArray(j)
+    ? isArr(j)
+    : isObj(j as JsonRecord)
diff --git a/test/Json.ts b/test/Json.ts
index 060baf731..3013b8732 100644
--- a/test/Json.ts
+++ b/test/Json.ts
@@ -30,4 +30,15 @@ describe('Json', () => {
 
     U.deepStrictEqual(_.stringify(undefined as any), E.left(new Error('Converting unsupported structure to JSON')))
   })
+
+  it('match', () => {
+    const t = () => true
+    const f = () => false
+    U.strictEqual(_.match(t, f, f, f, f, f)(null), true)
+    U.strictEqual(_.match(f, t, f, f, f, f)(true), true)
+    U.strictEqual(_.match(f, f, t, f, f, f)(32.2), true)
+    U.strictEqual(_.match(f, f, f, t, f, f)('dolphin'), true)
+    U.strictEqual(_.match(f, f, f, f, t, f)(['zebra', 'tiger']), true)
+    U.strictEqual(_.match(f, f, f, f, f, t)({ name: 'Toni', age: 35 }), true)
+  })
 })

From b3c0a7869825bb1a9fa7fdab7dd9b319bb332c83 Mon Sep 17 00:00:00 2001
From: Michael Bock <me@thought2.de>
Date: Fri, 25 Jun 2021 12:23:34 +0200
Subject: [PATCH 2/2] Use `on` instead of `is` in Json/match

---
 src/Json.ts | 26 +++++++++++++-------------
 1 file changed, 13 insertions(+), 13 deletions(-)

diff --git a/src/Json.ts b/src/Json.ts
index 9ea53e798..7e3f82a2c 100644
--- a/src/Json.ts
+++ b/src/Json.ts
@@ -87,21 +87,21 @@ export const stringify = <A>(a: A): Either<unknown, string> => stringifyJSON(a,
  *  @since 2.10.6
  */
 export const match: <Z>(
-  isNull: () => Z,
-  isBool: (x: boolean) => Z,
-  isNum: (x: number) => Z,
-  isStr: (x: string) => Z,
-  isArr: (x: Array<Json>) => Z,
-  isObj: (x: Record<string, Json>) => Z
-) => (j: Json) => Z = (isNull, isBool, isNum, isStr, isArr, isObj) => (j) =>
+  onNull: () => Z,
+  onBool: (x: boolean) => Z,
+  onNum: (x: number) => Z,
+  onStr: (x: string) => Z,
+  onArr: (x: JsonArray) => Z,
+  onObj: (x: JsonRecord) => Z
+) => (j: Json) => Z = (onNull, onBool, onNum, onStr, onArr, onObj) => (j) =>
   j === null
-    ? isNull()
+    ? onNull()
     : typeof j === 'boolean'
-    ? isBool(j)
+    ? onBool(j)
     : typeof j === 'number'
-    ? isNum(j)
+    ? onNum(j)
     : typeof j === 'string'
-    ? isStr(j)
+    ? onStr(j)
     : Array.isArray(j)
-    ? isArr(j)
-    : isObj(j as JsonRecord)
+    ? onArr(j)
+    : onObj(j as JsonRecord)